In Japan, the concentrations of hazardous substances which are potentially harmful to human health and may be contained in drainage water from factories or other sources are controlled under the Water Pollution Prevention Act. The concentrations of chemical substances contained in tap water are controlled under related regulations, such as the water quality criteria based on the Water Supply Act. Many other countries also have their own laws and regulations for controlling such chemical substances, although the kinds of substances to be controlled and criteria to be applied vary from one country to another. In order to determine whether or not those various regulations are properly met, it has been required to regularly conduct a test for hazardous substances in industrial effluent, environmental water (e.g. river water) or tap water.
According to the current practice, a water quality test for environmental water (e.g. river water) or industrial effluent is normally performed as follows: A person in charge of the test regularly visits the site (investigation site) and collects a sample of water. The sample is brought back to a research facility or the like, where the sample is initially subjected to a pretreatment for an analysis and is subsequently analyzed with an analyzing device. Examples of the commonly used analyzing devices include: a liquid chromatograph (LC), gas chromatograph (GC) as well as LC-MS and GC-MS in which a mass analyzer is used as the detector for LC or GC (see Patent Literature 1 or other documents). In the case where an LC-MS or GC-MS is used, a process for identifying a substance in a sample using a mass spectrum acquired by mass spectrometry is normally performed.
However, with the previously described conventional method, it is not easy to increase the frequency of the test, and it is difficult to deal with a sudden occurrence of the mixing of a hazardous substance. Therefore, a hazardous substance may be missed in the detection or the countermeasure may become too late due to a delayed detection.
Additionally, environmental water (e.g. river water) normally contains a wide variety of compounds other than the hazardous substances. Those compounds cannot be completely separated from the hazardous substances even with an LC or GC. Therefore, ion peaks originating from a plurality of compounds will be observed on a mass spectrum. An operator needs to perform the task of locating a peak originating from a hazardous substance from among a large number of peaks observed on the mass spectrum. Such a task is not only extremely cumbersome, but may also cause overlooking of the hazardous substance.